Inductively heated electrical contact furnace with preheater



July 7, 1953 c. c. sei-icm@ INDUCTIVELY HEAT ED ELECTRICAL CON FURNCEWITH PREHEATER Filed Dec. 1949 Patented July 7, 1953 INDUCTIVELY HEATEDELECTRICAL CON- IACT FURNACE WITH PREHEATER Carl Christian Schrg,Frankfurt am Main Hcchst, Germany Application December 15, 1949, SerialNo. 133,205

In contact furnaces having annnular shaped reaction chambers forcarrying out the chemical reactions, it is frequently the case thatuseful space is lost by taking in at too low a temperature cf the gaseswhich are to carry out the reaction in the furnace, and which first mustbe raised to the temperature at which the reaction takes place.

Attempts have been made to avoid this difficulty by conducting the gasesthrough a separately arranged pre-heater, wherein same are raised toapproximately the reaction temperature, before they enter the reactionfurnace itself. This method, it is true, accomplished the desiredresults, in production operation, but it unavoidably resulted in thedisadvantages that the furnace and pre-heater structure became morecomplicated, required more space, and a greater capital expenditure. Ithas also been attempted to avoid these disadvantages by providing theheated furnace with a short circuited secondary winding consisting of acoiled pipe, wherein the gases were raised to approximately the reactiontemperature by inductive heating before they entered the reactionchamber of the furnace. In this way, it was perhaps the case that asimple and somewhat inexpensive structure was provided. The disadvantagestill existed, however, that there was a fixed ratio of heat transfercapacity between the primary and secondary components, that is, betweenthe furnace and the pre-heater, whereas in actual practice this ratio isrequired to be variable within wide limits, a result that cannot beattained with the simple structure according to this arrangement.

According to the present invention the desired result may be attained byconstructing in the inner space of the annular chamber of a reactionfurnace an electrically energized preheater, which is preferably heatedaccording to the induction heating principle.

The arrangement according to the present invention is shown in verticalsection in Figure l; and,

Figure 2 is a cross-sectional view of the structure shown in Figure 1.

Referring now to the drawing in detail, the reference character Arepresents the annular reaction chamber of the contact furnace, whereinthe reactions take place. The exterior wall B of the furnace isinductively heated by the heat resistant windings C, which are energizedby the respective phases of a polyphase alternating current powersystem. A central conduit E In Germany December 20, 1948 1 claim. (c1.21e-47) is positioned in the inner part ofthe annular space, whichlatter is bounded on its outer periphery bythe wall D. Heat resistantcoils F are positioned intermediate the central conduit E and the wall Dand are respectively connected to the different phases of a polyphaseelectrical power system to effect heating by the inductive heatingprinciple. The space between the wall D and outer surface of the conduitE is determined so that the exciting coils F exactly t there. As thuspositioned, they are equally effective in heating the wall D. Theelectrical energy converted into heat must be sufficient for equalizingthe heat differential between the wall D and conduit E.

The interior G of the central conduit E constitutes the pre-heaterchamber and this is normally lled with granular material. The gases areadmitted to the pre-heater chamber G through a central tube H, which isconnected to the central conduit E, and are raised in the preheaterchamber to the reaction temperature or approximately thereto. They leavethe preheater chamber G under the cover J and pass to the annularchamber A, where the reaction takes place. From the annular chamber Athey are conducted from the furnace by pipes K.

For the purpose of obtaining the desired relative variations in thetemperatures of the preheater chamber G and the annular reaction chamberA, it is desirable that the coils F for the pre-heater chamber and thecoils C for the reaction chamber be separately energized.

The operation of the combined Contact furnace and pre-heater accordingto the present invention may be varied according to the load demandswithin wide limits. When carrying out exothermic processes, thesuperfluous heat, which is not used for carrying out the reaction isused for pre-heating; when carrying out endothermic processes, theheating from the inductor coils on both sides of the annular reactionchamber effects a very uniform reaction process. The heat resistantexciting windings, which effect the inductive heating, are put in andaround the furnace in the usual manner. Automatic controllers (notshown) may be provided for maintaining the thermal equilibrium.

If the chemical reaction process to be carried out should so require,the pre-heater chamber and the annular reaction chamber may beinterpositioned, the latter being placed on the outside of the furnaceand the former axially thereof, without departing from the principle ofthe invention. Also, the reaction process to be carried out may be theinverse of that described, that is, the gases may be directed from thetop into the pre-heater chamber and from below into the reactionchamber.

The electrical heating could also be accomplshed by resistance coils.Since, however, there is always present the danger of explosion incarrying 'out most production operations heating by the inductive effectis the preferred form.

Having now fully described my invention, what I claim as new and usefuland desire to secure by Letters Patent of the United States:

In an electrical heating furnace for carrying out high temperatureexothermic and endothermic reactions, a central pre-heating chamber, acentral conduit connected to said pre-heating chamber for conductinggases thereto, a 'plurality of inductor coils adapted to be connected,respectively, to the various phases of a polyphase power system closelysurrounding said pre- Lheating chamber in aligned .relationship,ranannular reaction chamber surrounding said preheating chamber closelypositioned with respect to the coils therearound, a cover over thecentral pre-heating chamber and the annular reaction chamber fordirecting the heated gases from the former reversely through the latter,and a plurality of inductor coils adapted to be connected, respectively,to the various phases of a polyphase power system closely surroundingsaid an- .nular reaction chamber in aligned relationship.

CARL CHRISTIAN SCHRG.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 1,078,619 Greene Nov. 18, 1913 1,356,818 Hadaway, Jr. Oct. 26,1920 .1,513,087 Buhl et al. Oct. 28, 1924 1,986,348 Lacy et al. Jan. l,1935 2,517,098 Dreyfus Aug. 1, 1950

